Wet deposition monitoring and modelling in New Brunswick — An area dominated by wet deposition due to long-range transport

Upper Mississippi Pb as a mid-1800s chronostratigraphic marker in sediments from seasonally anoxic lakes in Eastern Canada

“…Its detection in lakes from an extended area in Québec is consistent with studies, based on stable Pb isotope ratio measurements in lake sediments (Blais, 1996;Gallon et al, 2005) and in lichens (Carignan and Gariepy, 1995), which have consistently shown that important proportions of Pb deposited in Southern Québec Province originated from Eastern USA. Furthermore, back trajectory studies indicate that air masses from the Midwest and Eastern USA reach, in addition to Québec Province, Southern Ontario and the Canadian Maritime Provinces (Hopper and Barrie, 1988;Davis, 1993;Lin et al, 1997;Brook et al, 2002;Canada-USA report, 2004). Thus, we infer that the strong and sharp isotopic signal from the Mississippi Valley, which is easily extracted from sediment material with a dilute acid solution and measured with instruments now commonly found in analytical laboratories, should be widely employed in Eastern North America as a time-stratigraphic marker for the mid-1800s.…”

Sources and chronology of atmospheric lead deposition to a Canadian Shield lake: Inferences from Pb isotopes and PAH profiles

“…Air masses reaching the geographical area of Québec City often pass over emission sources located in the United States, largely from eastern and midwest states (Hopper and Barrie, 1988;Davis, 1993;Lin et al, 1997;Brook, 2002;Urquizo et al, 2003). Simonetti et al (2000a) reported that transport of Eurasian pollution over the high Arctic influenced the 206 Pb/ 207 Pb ratios measured in snow samples collected North of the 47°N latitude, but not in the St. Lawrence River Valley between Montréal and Québec City.…”

“…Atmospheric deposition therefore has been the only input of anthropogenic Pb to the lake. Back-trajectories of air masses determined from areas close to L. Tantaré indicate that the lake is under the influence of atmospheric emissions from the Midwest-Great Lakes and Eastern regions of the USA as well as from cities located along the St. Lawrence River (Hopper and Barrie, 1988;Davis, 1993;Lin et al, 1997;Brook et al, 2002;Urquizo et al, 2003). At the coring site, diagenetic processes such as bioturbation, bioirrigation, and postdepositional remobilization have a negligible influence on the solid-phase Pb profile (Gallon et al, 2004).…”